It's not bad. there are a lot of questions, like 2000+. i like that you can create customized tests, i.e specific topics, all topics, questions missed, questions not seen before, etc. it tracks your progress too, which is nice. also, it is relatively inexpensive at around $50 for 90 days.
my only problem so far is that the question selection is somewhat poor. meaning, say you want to do a 25 question test on hypertension, there will randomly be like 5-7 or so questions on statistical analysis, or something totally random like that. not a big deal, but kind of annoying. when you aren't prepared to answer those questions, it can bring down your average, making progress tracking less meaningful.